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UNCLASSIFIED
The fireball radius for this shot was considerably larger than the
height of the tower so that the fireball actually contacted the ground
surface in a circular area about 570 ft in diameter. Assuming that the
264 tons of coral sand which entered into the formation of the fallout
particles were removed evenly from this circular area and by using
1.25 g/ee as the bulk density of coral sand, it can be computed that a
layer of sand approximately 2 mm in thickness was removed. Of this thin
layer of sand only a small fraction was actually vaporized, the greater
part being only melted. This fraction was probably located near the
center of the circular area around the tower where most of the tracer
minerals had been placed which would account for the apparent vaporization
of a considerable part of the tracer minerals.
The fact that only a thin layer of sand was actually either vaporized
or melted, even though in contact with the fireball, and that even the iron
tower seems to have been incompletely vaporized indicates that the thermal
effects penetrate only superficially into solid material during the short
duration of the very high temperatures. By computing the energy required
to heat, decarbonate, and melt 264 tons of coral sand and to heat, melt,
and vaporize 165 tons of iron, and comparing this figure with the thermal
radiant energy liberated by a bomb of approximately the same size as this
shot,3 it is seen that only about 8.5 percent of the available thermal
radiant energy was utilized for heating the tower and soil materials. This
further indicates that the limiting factor in the heating of solid material
is not the heat energy available from the bomb but the finite thermal diffusivity of the solid material.
Approved by:
ER. Somp hind
E. R. TOMPKINS
Head, Chemical Technology Division
For the Scientific Director
13
UNCLASSIFIED
.